System and method for selectively limiting tractive effort to facilitate train control

ABSTRACT

Method for controlling the level of tractive efforts in a train having a first locomotive at a head end of the train, constituting a lead locomotive, and a second locomotive positioned in the train behind the lead locomotive, constituting a remote locomotive, with the remote locomotive being configured to selectively operate in either of two modes of operation, such as a first mode in which the locomotive operates at a full tractive effort level of operation and a second mode in which the locomotive operates in a partial tractive effort level of operation producing a tractive effort which is less than the full tractive effort of the locomotive. The method allows selecting (e.g., at the lead locomotive) one of the two modes of operation for producing a level of tractive effort appropriate for conditions as the train moves along a length of track. The method further allows transmitting a signal indicative of the selected mode of operation from the lead locomotive to the remote locomotive. The signal is received at the remote locomotive. The tractive effort generated at the remote locomotive is controlled so as not to exceed the selected level.

This application is a continuation of U.S. patent application Ser. No.10/354,638 filed Jan. 30, 2003 now U.S. Pat. No. 6,922,619 which in turnclaims the benefit of U.S. application Ser. No. 60/319,128 filed Feb.28, 2002 and is each herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The invention relates generally to locomotive propulsion systems and, inparticular, to locomotive controllers for selectively limiting tractiveeffort in locomotives.

Compared to earlier locomotives, such as locomotives equipped with a DC(direct current) propulsion system, locomotives equipped with an AC(alternating current) propulsion system generally produce at low speedssubstantially more tractive effort and provide higher adhesion to therails. When the locomotive is used for heavy hauling application, suchas the hauling of bulk materials, grain, etc., this high tractive effortis desirable. However, the high tractive effort provided by these highperformance locomotives, as may be part of a remote consist oflocomotives in a relatively light hauling application, could causelifting or derailment of one or more cars under certain conditions,particularly in curvy terrain. Examples of factors that may adverselyaffect operation of the train may include the presence of one or morelighter cars, uneven tonnage distribution, the presence of one or moreempty cars in the train, etc.

In view of the foregoing considerations, it would be desirable toprovide system and techniques that would enable a controllable reductionin locomotive tractive effort. This would avoid operation in modes ofhigh tractive effort to reduce the tendency of some of the railcars tolift from the rail tracks and hence avoid the possibility of derailment,such as could occur in the event the high tractive effort is notcommensurate with the actual characteristics of the train load, such asmagnitude of the load, uneven distribution of the load, etc. Thus, thisinvention in one aspect thereof, selectably reduces the maximum tractiveeffort generated by locomotives used in remote distributed powerapplications, while retaining their full horsepower at higher speedswhere tractive effort is typically reduced. It would be furtherdesirable to allow users of locomotive fleets to be able to quickly andreliably configure a locomotive capable of delivering high tractiveeffort for multiple applications, such as those where high tractiveeffort is required as well as for applications that otherwise would callfor lower rated locomotives.

BRIEF SUMMARY OF THE INVENTION

Generally, the present invention fulfills the foregoing needs byproviding in one aspect thereof, a method for controlling the level oftractive efforts in a train having a first locomotive at a head end ofthe train, constituting a lead locomotive, and a second locomotivepositioned in the train behind the lead locomotive, constituting aremote locomotive, with the remote locomotive being configured toselectively operate in either of two modes of operation comprising afirst mode in which the locomotive operates at a full tractive effortlevel of operation and a second mode in which the locomotive operates ina partial tractive effort level of operation producing a tractive effortwhich is less than the full tractive effort of the locomotive. Themethod allows selecting (e.g., at the lead locomotive) one of the twomodes of operation for producing a level of tractive effort appropriatefor conditions as the train moves along a length of track. The methodfurther allows transmitting a signal indicative of the selected mode ofoperation from the lead locomotive to the remote locomotive. The signalis received at the remote locomotive. The tractive effort generated atthe remote locomotive is controlled so as not to exceed the selectedlevel a method for remotely controlling the level of tractive effortproduced in at least one locomotive remote from a lead locomotive in atrain.

In another aspect thereof, the present invention further fulfills theforegoing needs by providing a system for remotely controlling the levelof tractive effort produced in at least one locomotive in a train. Thesystem includes a tractive effort mode selector configured to remotelyselect one of the following operational modes for the at least onelocomotive: a limited tractive effort mode and a full tractive effortmode. The system further includes a tractive effort processorconfigured, when selecting the limited tractive effort mode, to limitthe value of tractive effort in the at least one locomotive to a lesservalue of the full tractive effort normally supplied by said locomotive,wherein the lesser value of the full tractive effort is selected toavoid undesirable lifting conditions relative to a rail track where thetrain travels, the tractive effort processor further configured, whenselecting the full tractive effort mode, to command the tractive effortin the at least one locomotive to the values of full tractive effortnormally supplied by said locomotive.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention will becomeapparent from the following detailed description of the invention whenread with the accompanying drawings in which:

FIG. 1 illustrates in part a schematic representation of a train thatmay benefit from system and method embodying aspects of the presentinvention for selectably controlling the level of tractive effortproduced by one or more locomotives remote from a lead locomotive, withthe communications among the locomotives being wireless from consist toconsist and being via trainline connections and/or wireless within aconsist.

FIG. 2 is a block diagram of exemplary controllers that may be remotelyactuated for providing selectable control of tractive effort produced inthe locomotive.

FIG. 3 is a block diagram of an exemplary tractive effort processorincluding a tractive effort limiter for selectively limiting the levelof tractive effort produced by any given locomotive. In one exemplaryembodiment, the value of the tractive effort limit is selected to avoidundesirable lifting conditions relative to the rail tracks where thetrain travels.

FIG. 4 is an exemplary plot of tractive effort as a function oflocomotive speed including an exemplary tractive effort limit that mayenable a given class of locomotives to be used both for heavy haulingapplications as well as for applications that would traditionally callfor a different class of locomotives with lesser ratings of tractiveeffort.

DETAILED DESCRIPTION OF THE INVENTION

In one exemplary embodiment, a propulsion system controller 10 (PSC)onboard each locomotive may be responsive to tractive-effort controlsignals generated in response to commands wirelessly communicated withlocomotive communication equipment 12 (e.g., referred to in commerce asLocotrol® Distributed Power Communication Equipment) from a leadlocomotive 14 relative to a remote consist 16. By way of example,consist 16 is shown to be made up of a remote locomotive 20 and a traillocomotive 22. It will be appreciated that the present invention is notlimited to the consist arrangement shown in FIG. 1 since many otherconsist arrangements may be provided depending on the specific trainapplication. As will be described below, respective controllers on-boardeach locomotive, such as distributed power controller (DPC) 24, primarylocomotive controller 26 (CAX), the PSC controller and the communicationequipment may be configured with appropriate control algorithms toselectively limit the tractive effort provided by each locomotive of aconsist.

In one exemplary embodiment, whenever a pair of locomotive train lines(such as lines T/L 18 and T/L 19) is energized (High), each locomotivemay be limited to a lesser value of the total tractive effort that suchlocomotive is designed to provide. As shown in FIG. 4, in an exemplaryembodiment, the locomotive may be limited to approximately 110,000pounds of tractive effort for all six wheel-axles instead of the normal180,000 pounds of tractive effort. In the exemplary embodiment, thecommunication equipment may be configured by way of the DPC controlleronboard the remote locomotive to energize the train lines to initiatethe limited tractive effort (TE) mode of operation. In one exemplaryembodiment, the PSC controller 10 would detect when both train lines areactive and interpret this condition as a command for limited tractiveeffort operation. A reduced tractive effort command would then beimposed on the respective traction motor controllers (TMC) 28.

In order for a remote locomotive to reduce tractive effort, thatlocomotive would initially determine whether it is equipped (e.g., viahardware, software or both) to operate in a reduced tractive effortmode. For example, locomotives able to operate in reduced tractiveeffort mode could have either a hardware “strap” or a signal thatindicates that it is equipped with selectable tractive effortcapability. Similarly, a road number may be selected from a pre-definedlist of road numbers indicating that the unit is equipped withselectable tractive effort. In one exemplary embodiment, an appropriatecontroller may monitor both the road number of the locomotive and/or thepresence or absence of the hardware strap to determine whether or notthe locomotive is equipped to operate in a reduced tractive effort mode.At distributed power link time, the operator will select either the fulltractive effort or reduced tractive effort mode. If the reduced tractiveeffort mode is selected, the distributed power unit on-board the leadlocomotive would instruct the remote DPC to operate in the reducedtractive effort mode. Assuming the remote distributed power units areconfigured for reduced tractive effort operations, the DPC controller 24on-board the remote would then energize trainlines, such as trainlines18 and 19 (two trainlines may be used for redundancy). In one exemplaryembodiment, each locomotive in consist 16 would operate in reducedtractive effort when they detect that either or both of these trainlineshave been energized. Remote units that are equipped with the ability tooperate in reduced tractive effort may default to this mode of operationfor safety reasons. Remote units would return to normal levels oftractive effort when they detect that both trainline 18 and trainline 19are de-energized. For example, this could happen when the operatorselects the full tractive effort mode of operation at link time and theremotes receive the command from the lead unit to operate in fulltractive effort mode and both trainlines 18 and 19 are de-energized.

In one exemplary embodiment, the locomotive controller is configured torestrict the tractive effort, not necessarily the horse power deliveredby the locomotive. This allows normal performance at higher trainspeeds. As suggested above, two train lines may be used in order toprovide a redundant, safe connection. It will be appreciated by thoseskilled in that art, that many communication techniques includingwireless communication techniques may be used to communicate the desiredoperational mode. Thus, even though the table below makes reference toexemplary hard-wired lines, it will be appreciated that the presentinvention is not limited to hard-wired implementations since suchinformation may be readily transferred via wireless communication assuggested above.

T/L18 T/L19 Action 0 (Low) 0 (Low) Normal Tractive Effort (e.g., 180,000pounds) 1 (High) 1 (High) Tractive effort will be limited to lower valuee.g., 110,000 pounds ± 1800 lbs. 0 (Low) 1 (High) Fault will be logged &TE will be limited to [TL_TE_LIM] 1 (High) 0 (Low) Fault will be logged& TE will be limited to [TL_TE_LIM]

In operation, controlled tractive effort (CTE) is a feature thatautomatically reduces tractive effort of locomotives that may be used aspushers or pullers, or both, in distributed-power mode. It iscontemplated that one or more locomotives configured with CTE capabilitymay be placed at the rear of the train depending, for example, ontonnage and controlled by a lead locomotive equipped with thedistributed-power equipment, such as Locotrol distributed-powerequipment. It is further contemplated that if one or more pushers areused, each of them would be CTE-equipped and the controlling unit at thehead end could be any DP-equipped unit. For example, assuming anAC4400CTE locomotive is used in a pusher application indistributed-power mode, its tractive effort may be automatically reducedfrom 145,000 pounds at 11 mph to 110,000 pounds at 11 mph. The tractiveeffort reduction would essentially make the ACT4400CTE locomotiveequivalent to a Dash-9 locomotive in tractive effort, and thusadvantageously make such AC locomotive practical for applications suchas DP Push/Pull on freight trains that are used both in heavy haulingapplications and in lighter hauling applications. Thus, in one keyaspect of the present invention, users of fleets of locomotives may beable to mix and match the tractive effort of the locomotives to theactual needs of any given train without having to wait for an availablelocomotive model capable of delivering the required tractive effort.Thus, the user would be able to use locomotives such as the ACT4400 CTEin multiple applications, such as those applications traditionallyreserved for those locomotives as well as for applications where alesser rated locomotive (from the point of view of tractive effortcapability) would be used without having to wait for availability of thelesser rated locomotive. Thus, aspects of the present invention allowthe users of fleet of locomotives for efficiently increasing theversatility of operation of such fleets.

FIG. 3 is a basic block diagram used to facilitate understanding ofoperational aspects of the present invention. As shown in FIG. 3, atractive effort processor 50 includes a notch processor 52 configured togenerate a tractive effort consistent with a respective notch commandsupplied to the processor 52. A tractive effort limiter 54 is configuredto limit the tractive effort using, for example, a tractive effort limitstored in a memory 56. In operation, upon activation of trainlines TL18and TL19, the traction processor limits its total tractive effortreference in each motoring notch to the amount desired for limitedtractive effort operation. The tractive effort reference may then beappropriately distributed (e.g., using standard optimization techniques)to each wheel axle based on the performance capability of each axle.Each axle and processor essentially comprises a closed loop mechanismthat continuously processes feedback performance data, which is thenused to re-allocate the distribution of tractive effort to each axle tobest achieve the reference value of tractive effort. It will beappreciated that if axle capabilities are degraded due to conditionssuch as poor rail condition, thermal limitation or horsepowerlimitations, the reference may not be achieved even with optimalre-allocations of tractive effort to other axles. The operator may beinformed of the limited tractive effort mode of operation by way of asummary message that may be displayed in a suitable display unit. Thesummary message may provide information indicative of whether or nottractive effort reduction is enabled, such as “TE Limited: TE ReductionEnabled”.

While the preferred embodiments of the present invention have been shownand described herein, it will be obvious that such embodiments areprovided by way of example only. Numerous variations, changes andsubstitutions will occur to those of skill in the art without departingfrom the invention herein. Accordingly, it is intended that theinvention be limited only by the spirit and scope of the appendedclaims.

1. A method for controlling a level of tractive effort in a train havinga first locomotive constituting a command locomotive, operable through arange of engine power settings, and a second locomotive positioned inthe train at a spaced location from the command locomotive, said secondlocomotive constituting a command-follower locomotive, operable througha range of engine power settings, with at least one railcar beingpositioned between the command and command-follower locomotives, acommunication link between the command and command-follower locomotivesfor transmitting and receiving engine power control signals forcontrolling locomotive engine power settings and tractive effort controlsignals for controlling the level of tractive effort, and at least oneof the locomotives being configured to selectively operate in either oftwo modes of operation comprising a first mode in which said at leastone locomotive generates a different tractive effort than when said atleast one locomotive is in a second mode of operation, the methodcomprising; at the command locomotive selecting between the two modes ofoperation for producing a level of tractive effort appropriate forconditions as the train moves along a length of track; transmitting atractive effort control signal indicative of the selected mode ofoperation; receiving the tractive effort control signal at another ofsaid locomotives; and controlling the tractive effort generated at saidat least one locomotive so as to develop a differential in the tractiveeffort generated by the command and command-follower locomotives, withthe tractive effort generated at the command locomotive being differentthan that generated at the command-follower locomotive, in one of thetwo modes of operation, whereby with the command and command-followerlocomotives under power to operate in engine power settings to move thetrain in a given direction of travel, the differential in the tractiveeffort generated by the command and command-follower locomotives isselected to avoid an occurrence of a derailment condition that otherwisecan develop in a railcar between the command and command-followerlocomotives.